1. Field of the Invention
The present invention relates to a coating method of forming an insulating film by coating a coating liquid dispersed therein particles or colloids destined to be a starting material of a film component in a solvent on a surface of a substrate, and relates to a coating unit, an aging unit, and a solvent replacement unit, and a film coating apparatus for coating a film.
2. Description of the Related Art
As a method of forming an interlayer insulating film of a semiconductor device, CVD and thermal oxidation are well known. On the other hand, other than these, there is a method called a sol-gel method. In this sol-gel method, a coating liquid dispersed colloids of TEOS (tetra-ethoxy-silane; (Si(C2H5O)4) in an organic solvent such as ethanol solution is coated on a surface of a semiconductor wafer(hereinafter, simply refers to as wafer), the coated film, after being gelled, is dried, to obtain a silicon oxide film. The examples of this sol-gel method are disclosed in Japanese Patent Laid-Open Application Nos. HEI-8-162450 and HEI-8-59362.
Behavior in the course of change of the coated film in this sol-gel method is shown schematically in FIG. 10A through FIG. 10C. First, particles or colloids 100 of the TEOS, when coated on a wafer, are in a dispersed state in a solvent 200 (FIG. 10A). Then, this coated film, by being subjected to an basic atmosphere or to heating, is promoted in polycondensation and hydrolysis of the TEOS. As the result, the coated film is gelled to form a reticular structure of the TEOS 300 (FIG. 10B).
Next, in order to remove moisture in the coating liquid, the solvent in the coated film-is replaced by another solvent 400 of which boiling point is low and surface tension is small (FIG. 10C). By drying further thereafter, a coated film of a silicon oxide film is obtained.
Incidentally, a step of replacing the solvent shown in FIG. 10C is carried out to remove moisture. Further, the step of replacing with the solvent is carried out with an object to make the film hydrophobic. That is, since OH group is liable to absorb the moisture, the OH group combined to a terminal portion of Sixe2x80x94O bond is replaced by another organic substance by cleaning the film with, for instance, HMDS or the like.
Further, another object is to suppress collapse of a structure of the film by employing a solvent of smaller surface tension than ethanol so that a large force is not placed on the reticular structure of the TEOS when the solvent vaporizes.
Thus, there are an uncountable number of minute pores in the silicon oxide film formed by the sol-gel method, there comes in air. Therefore, relative dielectric constant of the oxide film xcex5 is close to that of air. Therefore, the electric resistance of the oxide film including such minute pores becomes such high as is close to that of air, resulting in an ideal insulating film.
In order to apply such a sol-gel method in an actual manufacturing line, a coating unit of coating a coating liquid on a wafer, an aging unit of gelling the coated film by heating the wafer at a pre-determined temperature, for instance, at 100xc2x0 C., and a replacement unit of replacing the solvent in the coated film by another solvent are necessary. Further, a pre-treatment unit for carrying out the pre-treatment such as hydrophobic treatment to the wafer, and a baking unit of drying the wafer are also necessary. And, by disposing a transfer mechanism of transferring the wafers between respective units, an apparatus is constituted.
Now, upon carrying out gelling treatment of the coated film, it is necessary that, through suppression of evaporation of the solvent from the coated film, gelling of the TEOS is made not to be disturbed. For this, it is not desirable to carry out gelling operation in an open system like the conventional method. Instead, the gelling treatment needs only to be carried out in a sealed container of an atmosphere filled with vapor of the solvent. That is, after disposing a wafer on a stage heated at a pre-determined temperature in the sealed container, gas including vapor of the solvent needs only to be introduced.
Now, the inventors of the present invention investigated to carry out the gelling operation with an aging unit 3 of a structure illustrated in FIG. 11, for instance. The aging unit 3 comprises a heating plate 30, a cover 33 provided with a heater, a gas introducing path 34, and a gas exhausting path 35.
As shown in FIG. 11, in this aging unit 3, the heating plate 30 is formed of ceramic and incorporates a heater 31a. 
The cover 33 is provided with a heater. This cover 33 is intimately connected to a circumference portion of the heating plate 30 through a sealing member 32, and, together with the heating plate 30, constitutes a sealed container defining a treatment chamber S.
In the heating plate 30, outside along the circumference portion of the wafer W, a gas introducing inlet 34a is formed in slit. This gas introducing inlet 34a penetrates the heating plate 30 and is connected to a gas introducing path 34 introducing gas from the outsides.
At the central portion of the cover 33, an exhausting outlet 35a is disposed. This exhausting outlet 35a penetrates the cover 33 to connect the exhausting path 35 communicating with the outsides. In addition, to the aging unit 3, 3 pieces of pins 36 for going up and down are disposed, for instance, and with these pins for going up and down, the wafer W is moved up and down between the heating plate 30 and the above position thereof.
As a gas to be employed here, a gas of a solvent component, for instance, vapor of ethylene glycol, is employed in order to suppress evaporation of the solvent inside the coated film during the atmosphere for heat treatment is heated.
And the gas introducing path 34 is disposed penetrating the heating plate 30. Therefore, the gas is introduced into the sealed container after being heated to approximately 100xc2x0 C., for instance, or a temperature extremely close to that temperature. At this time, the concentration of the vapor of ethylene glycol is a concentration that is equal with the saturated vapor pressure at a treatment temperature of approximately 100xc2x0 C., for instance. Further, in addition to ethylene glycol, a gas accelerating gelation, ammonia gas, for instance, can be introduced simultaneously.
However, in such a sealed container as the aging unit 3 shown in FIG. 11, when introduction of gas therein is started, there is such a problem that until supply of the gas reaches a steady state, the concentration and temperature of the gas fluctuate.
Also as aforementioned, in the case of a wafer being processed at a pre-determined temperature higher than normal temperature, 100xc2x0 C., for instance, when the wafer of the room temperature is transferred as it is into the sealed container of a pre-determined temperature, the gas of the solvent component which is at the saturated vapor pressure in the sealed container contacts with the wafer, to lower the temperature thereof. As the result, it becomes a super-saturated state, and the gas of the solvent component is likely to condense. When ethylene glycol, for instance, condenses on the wafer, the thickness of that part becomes thick, resulting in a problem of becoming a non-homogeneous insulating film.
The first invention of the present application is made to solve such a problem.
That is, an object of the first invention is to provide a method of coating a film which are capable of suppressing fluctuation of temperature and concentration at the starting time of gas introduction into a sealed container, capable of preventing the solvent component from condensation immediate after transfer of a substrate, for instance, an wafer into the sealed container, and capable of obtaining thereby a thin film, for instance, an interlayer insulating film, of an excellent quality, an aging unit, and an apparatus of coating a film.
For this, a method of coating a film of the first invention comprises the following steps as disclosed in claim 1:
a step of forming a film by coating a liquid, in which particles or colloids of a starting material of a film component is dispersed in a solvent, on a surface of a substrate;
a first gelling step of, in addition to transferring of the substrate into a sealed container, gelling the substrate in a state of the coated substrate being exposed to gas including vapor of the solvent of the coating liquid at a first average concentration; and
a second gelling step of gelling in a state where the insides of the sealed container is filled by a gas including the vapor of the solvent of the coating liquid at a second average concentration higher than the first average concentration.
Further, an aging unit for carrying out this method of forming the film comprises:
a treatment chamber accommodating a substrate thereon a film including a solvent and particles or colloids of starting material of a film component is formed;
a heater of heating the substrate;
a carrier gas feeding system feeding the carrier gas towards the treatment chamber;
a solvent dispensing system of dispensing the solvent towards the treatment chamber;
a mixing system forming a gas mixture containing vapor of the solvent from the carrier gas feeding system and the solvent dispensing system; and
an adjusting mechanism for adjusting concentration of the solvent in the gas mixture.
Further, an apparatus of forming a film for carrying out the aforementioned method of forming the film comprises:
a coating unit of coating a liquid in which particles or colloids of a starting material of a film component is dispersed on a surface of a substrate;
an aging unit comprising a treatment chamber accommodating a substrate thereon a film is formed, a heater heating the substrate, a carrier gas feeding system feeding a carrier gas towards the treatment chamber, a solvent dispensing system dispensing the solvent towards the treatment chamber, a mixing system forming a gas mixture containing vapor of solvent from the carrier gas feeding system and the solvent dispensing system, an adjustment mechanism adjusting concentration of the solvent of the gas mixture, and
a solvent replacement unit replacing the solvent in the coated film.
In the aforementioned method, the gas introduced into the sealed container in the first gelling step is preferable to be adjusted in temperature to approximately a temperature of the inside of the sealed container.
According to the first invention, after a substrate is transferred into a sealed container until the temperature of the substrate reaches the pre-determined temperature, the average concentration of the solvent component is made low. On the other hand, when the temperature of the substrate becomes high, the concentration of the solvent component is made high. Therefore, immediate after the substrate is transferred into the sealed container, the gas of the solvent component can be prevented from condensation.
Incidentally, before transferring the substrate into the sealed container, it is preferable that while a mixture of vapor of the solvent component and a carrier gas is formed, the gas mixture is being exhausted. By implementing like this, the fluctuation of the concentration of the solvent component and the temperature can be suppressed at the starting of gas introduction.
Specific examples of the first invention are cited as follows. A step of gelling particles or colloids of the coated film is one that heats the substrate. Further, the gas to be introduced into the sealed container is made by mixing a carrier gas and the vapor of the solvent component. The first gelling step is carried out by adjusting the flow rate of at least one of the carrier gas or the vapor of the solvent component. Further, mixing of the carrier gas and the vapor of the solvent component is carried out at an evaporator which evaporates liquid of the solvent component. The first gelling step is carried out by adjusting the flow rate of the liquid of the solvent component being introduced into the evaporator.
In this case, the first gelling step includes the step of varying continuously the concentration of the vapor of the solvent component. Further, the first gelling step includes the step of mixing intermittently the vapor of the solvent component with the carrier gas.
Further, the second gelling step includes the step of, after the first gelling step is carried out subsequent transfer of the substrate into the sealed container, feeding the gas into the sealed container in a state where the average concentration of the vapor of the solvent component is higher than that during the first gelling step.
Further, an average concentration of the solvent of the gas being exposed to the substrate at each step is preferable to be the concentration corresponding to the saturated vapor pressure at the substrate temperature at each step. For instance, the aforementioned first average concentration is preferable to be the concentration corresponding to the saturated vapor pressure at the substrate temperature at the time of introduction of the container, the second average concentration being preferable to be the concentration corresponding to the saturated vapor pressure at the substrate temperature during gelling.
The reason is that there is a problem that, when the average concentration of the solvent in the gas is lower than the saturated vapor pressure, the solvent volatilizes from the coated film on the substrate, resulting in difficulty of generating pores in the film.
On the other hand, when the average concentration of the solvent in the gas is higher than the saturated vapor pressure, there is a problem that the vapor condenses on the substrate or on the wall of the treatment chamber, the condensation on the substrate induces deterioration of the film quality, and the condensation on the wall of the treatment chamber tends to cause contamination of the apparatus or re-sticking on the substrate.
Next, as the second invention, the inventors investigated to form an interlayer insulating film by use of sol-gel method illustrated in FIG. 10A to FIG. 10C.
Here, the inventors further attempted to replace the solvent in the coated film by another solvent 400 (FIG. 10C). In this replacement step of the solvent, after replacement of water in the coated film by ethanol, for instance, HMDS (hexamethyl disilane) is supplied to remove OH group, and finally replacement by heptane is carried out.
The reason for employing heptane here is to suppress collapse of the film structure by avoiding, with use of a solvent of low surface tension, a large power placed on a reticular structure of TEOS during vaporization of the solvent.
When applying such a sol-gel method into an actual manufacturing line, a coating unit for coating a coating liquid on a wafer, a gelling unit for gelling the coated film and a replacement unit for replacing the solvent in the coated film by another solvent are necessary.
In the replacement step of the solvent, because of use of 3 solvents as aforementioned, the present inventors attempted to employ a conventional resist coating device for the replacement unit.
The resist coating device will be described with reference to FIG. 18.
The device comprises a vacuum chuck 194 which is capable of going up and down and rotates a wafer while holding in a horizontal position, a fixed cup 195, and a nozzle 196 for dispensing a solvent to the wafer. The fixed cup 195 is disposed such that it surrounds the wafer W on the chuck 194, and an opening portion at an upper surface is opened or closed by the cup 195a. 
As the nozzle 196, 3 pieces of nozzles 196a to 196c which discharge ethanol, HMDS and heptane, respectively, are disposed. These nozzles of 196a to 196c are taken out in this order by grasping by a carrying arm 197 from nozzle receiving portions 198a to 198c, and are transferred up to around the central portion above the wafer W.
In the case of carrying out the solvent replacement step of the sol-gel method with such an apparatus, first, in a state where the cover 195a is open, the wafer W is transferred to the chuck 194. Then, ethanol is dripped from the nozzle 196a onto the wafer W, thereafter the fixed cup 195 is closed, the wafer W is rotated. Thus, the ethanol is diffused over the whole front surface of the wafer W through centrifugal force. Thereafter, the cover 195a is opened, similarly HMDS is supplied on the surface of the wafer W with the nozzle 196b. Then, heptane is further supplied on the surface of the wafer W through the nozzle 196c, to carry out treatment.
However, in the aforementioned apparatus, since 3 pieces of nozzles 196 prepared for the respective solvents are grasped by a carrying arm 197 to transfer, when the solvent is supplied on the surface of the wafer W, after transfer by the nozzle 196a, the nozzle 196b is necessary to be transferred. That is, the carrying arm 197 was required to repeat to go and return several times between the nozzle receiving portion 198 and a position above the wafer W. Further, each time one solvent is diffused on the wafer W, the cover 195a of the fixed cup 195 was necessary to be opened and closed.
Thus, the next solvent is impossible to be supplied continuously succeeding the supply of one solvent, supply of the solvent is stopped to cause idle time.
Moreover, since until next supply of the solvent, a travelling time of the carrying arm 197 and an opening/closing time of the cover 195a are piled up, a certain degree of time is necessary.
When it takes time between replacements of the solvents and there is an idle time of the supply of the solvent, the solvent on the surface of the wafer, for instance, contacts with the air. Therefore, there occurs such an inconvenience as that moisture in the air is confined in the film. And, as the result, the formed interlayer insulating film is deteriorated in its film quality.
The second invention of the present application was made to solve such a problem.
That is, an object of the second invention of the present application is to provide, in a method of forming a film having a step of carrying out replacement of solvents by dispensing successively at least a plurality of solvents on a surface of a substrate thereon a coated film is to be formed, a method of forming a film, a solvent replacement unit, and an apparatus for forming a film in which a preceding solvent and a succeeding solvent can be supplied continuously, thereby enabling to obtain an excellent thin film such as an interlayer insulating film.
Therefore, a method of forming a film of the second invention comprises the following steps disclosed in claim 13:
a step of forming a film on a surface of a substrate by coating a coating liquid in which particles or colloids of a starting material of a film component are dispersed in a solvent;
a step of gelling the particles or the colloids in the coated film; and
a step of dispensing at least 2 kinds of replacement solvents different from the aforementioned solvent on the surface of the substrate by switching successively;
wherein the switching of the replacement solvent to be supplied is carried out by starting dispensing of the succeeding solvent while dispensing the preceding replacement solvent, and thereafter by stopping supply of the preceding replacement solvent.
Further, a solvent replacement unit for carrying out this method of coating a film comprises:
a treatment vessel accommodating a substrate formed thereon a film containing the solvent and particles or colloids of the starting material of the film component;
a spin chuck holding the substrate disposed in the treatment vessel;
a plurality of solvent supply systems dispensing solvents towards the substrate; and
a switching device for switching the plurality of solvent dispensing systems.
Further, an apparatus of forming a film for carrying out the aforementioned method of forming a film comprises:
a coating unit forming a film on a surface of a substrate by coating a liquid in which particles or colloids of the starting material of the film component are dispersed in a solvent;
an aging unit for gelling the coated film; and
a solvent replacement unit consisting of a treatment vessel accommodating a substrate formed thereon a film containing the solvent and particles or colloids of the starting material of the film component, a spin chuck holding the substrate disposed in the treatment vessel, a plurality of solvent supply systems dispensing solvents to the substrate, and a switching device switching the plurality of solvent supply systems.
In the method of the second invention, since the supply of the succeeding solvent begins before the supply of the preceding solvent is ceased, the preceding solvent and the succeeding solvent are continuously supplied on the surface of the coated film without being interrupted. Thus, in the solvent replacement step, there is no time of interruption of supply of the solvent on the surface of the substrate thereon the coated film is formed. Therefore, occurrence of such an inconvenience as that occurs due to stoppage of the supply of the solvent, inclusion of moisture in the coated film, for instance, can be suppressed, resulting in formation of an excellent thin film on the substrate.
In the second invention, in the solvent replacement step, among the plurality kinds of solvents, at least 2 kinds of solvents may be supplied on a substrate from a common solvent dispensing portion, each of the plurality of kinds of solvents may be supplied on the substrate from separate solvent dispensing portions. Further, in the solvent replacement step, alcohol, a liquid for hydrophobic treatment, and a solvent of smaller surface tension than the solvent contained in the coating liquid, for instance, are supplied in this order on the substrate.
Next, as the third invention, the inventors attempted to use spin coating, which is used in coating of resist, as a coating method. In this unit, on the central portion of the wafer sucked to a spin chuck, the coating liquid is dripped, the spin chuck is rotated to thin out the coated film over the whole surface through centrifugal force to coat.
Now, since, during coating of a coating liquid, the wafer is rotated with high speed, air flow is generated along the surface of the wafer, resulting in speedy evaporation of the solvent in the coating liquid. Therefore, evaporation of the solvent is being tried to be suppressed by adjusting the temperature and humidity of the coating unit and the temperature of the coating liquid. However, it is difficult to suppress sufficiently the evaporation of the solvent through only adjustment of their temperature and humidity. In addition, when the solvent evaporates much, gelling of the solvent is disturbed to deteriorate the film quality of the silicon oxide film.
The third invention of the present application was made to solve such a problem.
That is, an object of the third invention is to provide a method of forming a film, a coating unit, and an apparatus of forming a film which, when obtaining a film by coating a coating liquid dispersed therein starting material of film components of colloids or particles in a solvent on the substrate, enable to obtain a thin film of excellent quality such as an interlayer insulating film.
For this, the third method of forming a film comprises the following steps as disclosed in claim 19:
a step of forming a film by coating a coating liquid, in which particles or colloids of the starting material of a film component are dispersed in a solvent, on a surface of a substrate under an atmosphere filled by the vapor of the solvent; and
a step of gelling the particles or colloids in the coated film;
wherein the vapor of the solvent contains one vapor of any one of solvent components.
As an example of a method of the third invention, a method of forming a film comprising the following steps can be cited:
a step of transferring a substrate into a treatment vessel from an inlet;
a step of closing the inlet of the treatment vessel;
a step of filling the treatment vessel with vapor of a solvent;
a step of coating a coating liquid in which particles or colloids of the starting material of the film component are dispersed in the solvent on the surface of the substrate in the treatment vessel filled by the vapor; and
a step of gelling the particles or the colloids in the coated film.
As another example of the method of the third invention, a method of forming a film comprising the following steps can be cited:
a step of disposing a substrate on a rotary stage by transferring into the treatment vessel from the inlet;
a step of closing the substrate inlet of the treatment vessel;
a step of filling the vapor by feeding vapor of the solvent into the treatment vessel;
a step of, together with rotating a rotary stage, spreading a coating liquid on the surface of the substrate by dispensing the coating liquid, in which particles or colloids of the starting material of the film component are dispersed in the solvent, on a surface of the substrate; and
a step of gelling the particles or the colloids in the coated film.
Further, a coating unit for carrying out this coating method comprises:
a treatment vessel accommodating a substrate;
a spin chuck holding the substrate disposed in the treatment vessel;
a coating liquid nozzle dispensing a coating liquid on the substrate;
a coating liquid supply system dispensing a coating liquid, in which particles or colloids of starting material of film component are dispersed in the solvent, to the coating liquid-nozzle;
a solvent nozzle dispensing the solvent into the treatment vessel; and
a solvent supply system dispensing the solvent to the solvent nozzle.
Further, an apparatus of forming a film for carrying out the aforementioned film forming method comprises:
a coating unit forming the film on the substrate comprising a treatment vessel accommodating a substrate, a spin chuck holding the substrate disposed in the treatment vessel, a coating liquid nozzle dispensing the coating liquid to the substrate, a coating liquid supply system dispensing a coating liquid, in which particles or colloids of the starting material of film component are dispersed in the solvent, to the coating liquid nozzle, a solvent nozzle dispensing the solvent into the treatment vessel, and a solvent dispensing system dispensing the solvent to the solvent nozzle;
an aging unit for gelling the coated film; and
a solvent replacement unit replacing the solvent in the coated film.
The third invention, after a film is formed on a surface of a substrate, while keeping an atmosphere therein the substrate is placed an atmosphere filled with vapor of the solvent, on the circumference portion of the substrate, a cleaning liquid of removing the coated film may be supplied to remove the coated film of the circumference portion.
In this case, the solvent contains a plurality kinds of organic solvents. The third invention includes the case where the vapor is at least one vapor of the plurality kinds of organic solvents.
For instance, the solvent contains ethylene glycol and alcohol, the vapor of the solvent is ethylene glycol. The starting material of the film component is a metal alkoxide, for instance.
Next, as the fourth invention, the inventors attempted to apply the aforementioned sol-gel method in an actual manufacturing line. That is, the inventors attempted to form a film by, in the step of forming a film, dispensing a coating liquid, in which particles or colloids of TEOS are dispersed in the solvent, on an approximately center of rotation of the wafer surface, then by rotating the wafer around a vertical axis, thereby spreading a coating liquid over the whole surface of the wafer by making use of centrifugal force of rotation.
Now, after the coating liquid is coated on the wafer, vaporization of the solvent is required to be suppressed not to disturb gelling of TEOS. For this, as one solvent components of the coating liquid, a solvent, which has a high boiling point and is difficult to evaporate, such as ethylene glycol, is employed.
However, because of high viscosity of ethylene glycol, use of it as the solvent causes the viscosity of the coating liquid itself.
On the other hand, on the surface of the wafer thereon an interlayer insulating film is formed, due to disposition of aluminum wiring, there is fine unevenness. Therefore, only by rotating the wafer after supply of the coating liquid on the surface of the wafer as described above, the coating liquid is difficult to spread due to its viscosity. Accordingly, the coating liquid is difficult to come into the fine unevenness of the surface of the wafer, thus, there occurs a problem that a film is difficult to be coated on the whole surface of the wafer. In recent years, in particular, finer pattern is a trend. As the trend of the fine pattern advances and the width of aluminum wiring becomes narrow, the coating liquid is the more difficult to come into.
The fourth invention of the present application was carried out to solve such a problem.
That is, an object of the fourth invention is to provide a method of forming a film, a coating unit, and an apparatus of forming a film in which the coating liquid is easily coated on the surface of the substrate, thereby a film is formed universally all over the surface of the substrate, as a result, an excellent thin film such as an interlayer insulating film can be obtained.
For this, a method of forming a film of the fourth invention comprises the following steps as disclosed in claim 26:
a step of coating the solvent of lower viscosity than the most viscous component among the solvent components of the coating liquids in which particles or colloids of the starting material of the film component are dispersed in a solvent, and of capable of dissolving the starting material, on the surface of the substrate;
a step of forming a film by coating the coating liquid on the surface of the substrate; and
a step of gelling particles or colloids in the coated film.
Here, as a starting material, tetraethoxysilane can be employed. Further, after the step of gelling, on the surface of the substrate thereon a film is formed, the other solvent than the aforementioned one is supplied, thereby the solvent replacement step for replacing the solvent in the coated film by the different solvent may be carried out.
Further, a coating unit for carrying out this film forming method comprises:
a treatment vessel accommodating a substrate;
a spin chuck holding the substrate disposed in the treatment vessel;
a solvent nozzle dispensing solvent to the substrate;
a solvent supply system dispensing the solvent to the solvent nozzle;
a coating liquid nozzle dispensing the coating liquid to the substrate thereto the solvent is supplied; and
a coating liquid supply system dispensing the coating liquid in which particles or colloids of the starting materials of film components are dispersed in the solvent to the coating liquid nozzle.
Further, an apparatus of forming a film for carrying out the aforementioned method for forming a film comprises:
a coating unit comprising a treatment vessel accommodating a substrate, a spin chuck holding the substrate disposed in the treatment vessel, a solvent nozzle dispensing solvent to the substrate, a solvent supply system dispensing solvent to the solvent nozzle, a coating liquid nozzle dispensing coating liquid to substrate thereto the solvent is supplied, and a coating liquid supply system dispensing the coating liquid in which particles or colloids of the starting materials of film components is dispersed in the solvent to the coating liquid nozzle;
an aging unit for gelling the coated film; and
a solvent replacement unit for replacing the solvent in the coated film.
In the method according to the fourth invention, in the step of forming a film, before coating a coating liquid on a substrate, a solvent of smaller viscosity than that of the component of the most highest viscosity among the components of solvent of the coating liquid is coated over the~whole surface of the substrate. Accordingly, when the coating liquid is supplied on the surface thereof, first, the starting material of the coating liquid and water are dissolved in the solution coated over the whole surface of the substrate.
Thereby, due to mixing of the coating liquid and the solution, the viscosity of the coating liquid becomes low. Accordingly, the coating liquid becomes easy to spread on the substrate, to be coated over the whole surface of the substrate universally. As the result, a thin film of excellent quality can be formed.
According to the method of the fourth invention, as a solution to be coated on a surface of a substrate before coating the coating liquid on the surface of the substrate, one component of lower viscosity than the highest one among the aforementioned components of the solvent may be employed. In this case, since one solvent component is coated, when the coating liquid is applied, this component and the coating liquid are likely to be easily mixed. And, upon mixing thereof, there is no occurrence of bubbles, accordingly a coated film of more excellent quality can be formed. Further, as a solution to be coated on the surface of the substrate preceding the step of applying the coating liquid on the surface of the substrate, alcohol can be employed. Since alcohol can dissolve the aforementioned starting materials and water, effect as identical as the aforementioned method of the first disclosure of the fourth invention can be obtained.
Next, as the fifth invention, the inventors have studied a method of forming an interlayer insulating film by use of the aforementioned sol-gel method.
In the case of applying the aforementioned sol-gel method in an actual manufacturing line, in the step of forming a film, the coating liquid is supplied approximately the center of rotation on the surface of the wafer, then the wafer is rotated. Thus, by spreading the coating liquid over the whole surface of the wafer by use of the centrifugal force of rotation, a film is formed. In this case, the coating liquid is made by mixing TEOS and the solvent in advance, the mixed liquid (coating liquid) is stored in a tank or the like, and the stored coating liquid is supplied on the surface of the wafer.
However, in the case of a film being formed with the coating liquid formed in advance and stored in a tank, there are some cases where unevenness of the film thickness or film quality is confirmed by eye-inspection. According to observation by the inventors, in the case of the coating liquid which has stood for a certain degree of time period after mixing of TEOS and the solvent being coated on the wafer, deterioration of the film quality was experientially confirmed to occur. This is a problem.
The fifth invention of the present application was made to solve such a problem.
That is, an object of the fifth invention is to provide a method of forming a film which can suppress deterioration of the film quality of the coated film, as a result, can obtain a thin film such as an interlayer insulating film of excellent quality.
For this, a method of forming a film of the fifth invention comprises the following steps as disclosed in claim 32:
a step of mixing a first liquid containing particles or colloids of a starting material of a film component which is insoluble or difficult to be dissolved in water and water, and a second liquid consisting of an organic solvent which can dissolve water and the film component;
a step of coating, after completion of the aforementioned mixing, before lapse of time in which the quality of the film obtained by the mixing deteriorates, the mixed liquid containing the first liquid and the second liquid on the surface of the substrate; and
a step of gelling the particles or the colloids in the film coated on the substrate.
According to the method of the fifth invention, after mixing of the first liquid and the second liquid, before lapse of the time period where the film quality of the obtained coated film deteriorates, within 6 min. after mixing for instance, the coating liquid is coated on the surface of the substrate. Thereby, the film quality of the coated film can be suppressed from deterioration, resulting in an excellent thin film such as a silicon oxide film.
In this fifth invention, after a step of coating the mixed liquid which does not stand the deterioration time of the film quality after completion of mixing of the first and the second liquids, before coating of the mixed liquid on the surface of the next substrate, a step of cleaning the mixing portion of the first and second liquids and the insides of the liquid path at the down-stream of the mixing portion with an organic solvent such as alcohol may be carried out.
In this case, the mixed liquid which remained in the liquid path and lapsed the film quality deteriorating time after mixing is cleared away by the organic solvent. Therefore, upon treatment of the next substrate, the old mixed liquid remaining in the liquid path is not coated, accordingly deterioration of the film quality can be suppressed.
Further, when alcohol is employed as the organic solvent, since alcohol dissolves the starting materials of the film components and water, cleaning of the insides of the liquid path can be carried out readily.
Next, as the sixth invention, the inventors have studied another method of forming a film with use of the aforementioned sol-gel method.
That is, in the aforementioned sol-gel method, after coating of the coating liquid on the wafer, by standing for one night, for instance, the coated film is gelled. However, for mass production, gelation should be carried out as fast as possible. As one method for this, heating of the wafer may be one candidate, however, in this case, the solvent in the coated film is activated in evaporation.
For this, the inventors have studied, as the sixth invention, of carrying out gelation at, for instance, room temperature with use of ammonium gas (NH3) containing water vapor.
The reason of containing moisture in ammonium gas is as follows. That is, a part of ammonium gas containing water vapor, upon sticking on the coated film, is ionized such as
NH3+H2Oxe2x86x92NH4++OHxe2x88x92.
That is, under presence of water, hydroxide group is formed to be basic. An alkali is a catalyst accelerating polycondensation and contributes to gelation. From this, water vapor is necessary to be contained. And, as the state approaches the saturated state due to much water vapor, OH groups can be expected to be generated much, accordingly the rate of gelation is considered to be fast.
In FIG. 35, a device being used when gelation is carried out with ammonium gas containing water vapor close to the saturated state is illustrated.
The device 501 comprises a disposing stage 511 of an wafer W, a treatment vessel 510 capable of tight sealing consisting of a sealing member 512 and a cover 513, a tank 521 storing commercial ammonia water (NH40H)(concentration of ammonia: 30% by weight at normal temperature) 520, a bubbling gas supply pipe 522 of carrying out bubbling by introducing ammonia gas into ammonia water 520 in the tank 521, an exhausting outlet 523 of exhausting the treatment gas generated by bubbling, and a piping 525 communicating the exhausting outlet 523 and the gas introducing inlet 514 disposed at the disposing stage 511.
At normal temperature, ammonia water contains approximately 33% by weight of ammonia as saturated concentration. Therefore, if the bubbling is started at normal temperature with the commercial ammonia water as it is, first, ammonia gas is absorbed in the ammonia water. During this, ammonia gas is not generated or is not generated enough to obtain desired flow rate if generated, accordingly gelation takes a long time. And, when the concentration of ammonia in the ammonia water attains approximately 33% by weight, the ammonia gas containing water vapor of approximately saturated concentration is generated as a treatment gas. The generated treatment gas is introduced into the treatment vessel 510 through the piping 525 and is exhausted out through an exhausting path 515 opened at a cover 513 of the treatment vessel 510.
However, in this device, as mentioned above, the commercial ammonia water is employed as it is. Therefore, when continuous treatment of the wafer is implemented, if ammonia water 520 in the tank 521 is replenished, the concentration of the ammonia water 520 is temporarily lowered and ammonia gas is absorbed. Accordingly, ammonia gas is not generated or, if generated, the desired flow rate can not be obtained. Therefore, there is a problem that gelation can not be completed, accordingly, the desired film thickness and film quality can not be obtained.
As a method preventing this from occurring, such a method is considered that, immediately before replenishment of ammonia water, gelling treatment is interrupted, and, after the treatment gas begins to be generated again, gelling is started again. However, upon carrying out like this, there occurs a problem that serviceability ratio of the device goes down, thereby through-put also goes down.
The sixth invention of the present application is made to solve such a problem.
That is, an object of the sixth invention is, upon gelling the coated film with an ammonia gas, to provide a gas treatment method capable of carrying out stable treatment, and capable of treating evenly between subjects to be treated.
Another object of the sixth invention is to provide a method capable of carrying out stable treatment, without restricting in the case of carrying out gelling treatment with an ammonia gas, also in the case of carrying out treatment to the subjects to be treated with the treatment gas.
For this, the method of forming a film of the sixth invention comprises the following steps as disclosed in claim 36:
a step of forming a film by coating a coating liquid, in which particles or colloids of a starting material of a film component is dispersed in a solvent, on a surface of a substrate; and
a step of gelling the particles or colloids in the coated film by exposing the substrate to the ammonia gas;
wherein in the step of gelling, an ammonia gas is generated by successively introducing the ammonia gas into at least 2 vessels accommodating ammonia water of ammonia concentration lower than the saturated concentration, the ammonia gas generated precedently is supplied to the substrate, thereafter the succeedingly generated ammonia gas is supplied to the substrate, thereby conductance of the ammonia gas supplied to the substrate is maintained constant.
Further, an aging unit for carrying out the method of forming a film comprises:
a treatment vessel accommodating a substrate;
a plurality of ammonia containers accommodating ammonia water;
bubbling gas supply systems feeding a carrier gas for bubbling in the respective ammonia containers;
bubbling gas valves closing or opening the respective bubbling gas supply systems;
exhausting systems for exhausting gas generated in the respective ammonia containers;
exhausting system valves for closing or opening the respective exhausting systems;
ammonia gas supply systems for feeding gas generated at the respective ammonia containers to the treatment vessels;
ammonia gas valves closing or opening the respective ammonia gas supply systems; and
a means for opening the respective bubbling gas valves in turn, at the same time, synchronizing with this closing or opening of the respective bubbling gas valves, closing respective exhausting system valves in turn, and opening the respective ammonia gas valves in turn.
Further, an apparatus of forming a film for carrying out the aforementioned method of forming a film comprises:
a coating unit for coating a coating liquid on a substrate;
an aging unit comprising a treatment vessel accommodating a substrate, a plurality of ammonia containers accommodating ammonia water, bubbling gas supply systems feeding a carrier gas for bubbling to the respective ammonia containers, bubbling gas valves closing or opening the respective bubbling gas supply systems, exhausting systems for exhausting gas generated from the respective ammonia containers, exhausting system valves for closing or opening the respective exhausting systems, ammonia gas supply systems feeding the gas generated at the respective ammonia containers to the treatment vessel, ammonia gas valves closing or opening the respective ammonia gas supply systems, and a means which opens in turn the respective bubbling gas valves, at the same time, synchronizing with closing or opening of the respective bubbling gas valves, closes in turn the respective exhausting system valves, and opens in turn the respective ammonia gas valves; and
a solvent replacement unit for replacing the solvent in the coated film.
Here, since the concentration of ammonia in ammonia water is lower than the saturated concentration, when ammonia water is replenished, ammonia gas, upon bubbling by it, is absorbed by ammonia water for a while. Therefore, it takes some time for ammonia gas containing vapor of moisture to be generated with stability.
According to the sixth invention, when ammonia water is replenished in the precedent container, the first container, for instance, ammonia gas is being generated from the succeeding container, the second container, for instance, accordingly supply of the ammonia gas containing vapor of moisture is not interrupted, thereby stable treatment can be carried out.
Further, by equalizing conductance of the path when gas flows from the precedent container through the treatment vessel, conductance of the path when gas flows from the precedent container through the first exhausting path, conductance of the path when gas flows from the succeeding container through the treatment vessel, and conductance of the path when gas flows from the succeeding container through the second exhausting path, upon switching the path, fluctuation of flow rate and pressure of ammonia gas can be suppressed. Therefore, more stable treatment can be carried out.
Further, a method of forming a film of the sixth invention comprises the following steps as disclosed in claim 41:
a step of forming a film by coating a coating liquid, in which particles or colloids of a starting material of a film component is dispersed in a solvent, on a surface of a substrate; and
a step of gelling the particles or the colloids in the coated film by exposing the substrate to ammonia gas;
wherein the gelling step comprises:
a preliminary exhausting step of exhausting treatment gas from gas source without going through the treatment vessel but through the exhausting path;
a step of transferring the subject to be treated into the treatment vessel; and
a treatment step of treating a subject to be treated by feeding the treatment gas from the gas source into the treatment vessel by switching the path from the exhausting path to treatment vessel side;
wherein the conductance of the path upon flowing through the treatment vessel from the gas source and conductance of path upon flowing through exhausting path are made equal.
According to the sixth invention, fluctuation of the flow rate and pressure of the gas can be suppressed when the path of the gas is switched, accordingly stable treatment can be carried out.
Next, the seventh invention will be described.
When the sol-gel method as described above is being applied in an actual manufacturing line, a coating unit for coating a coating liquid on an wafer, a gelling unit for gelling the coated film, and a replacement unit for replacing the solvent in the coated film by another solvent are necessary.
In addition, a pre-treatment unit for carrying out pre-treatment such as hydrophobic treatment to the wafer, and a bake unit for drying the wafer are also necessary. The device is constituted by further disposing a transferring mechanism for transferring the wafer between respective units.
Now, when the coating liquid is coated on the wafer, the solvent, being organic solvent, evaporates. If the amount of evaporation is much, there is a problem that the aimed film thickness and film quality can not be obtained.
The seventh invention of the present application is made to solve such a problem.
That is, an object of the seventh invention is to provide an apparatus for forming a film capable of carrying out the following step as soon as possible after coating a coating liquid in which particles or colloids of a starting material of a film components are dispersed in a solvent on a substrate and capable of obtaining an excellent thin film such as interlayer insulating film, for instance.
Therefore, the apparatus of forming a film of the seventh invention comprises, as disclosed in claim 44: a coating portion of forming a film by coating a coating liquid, in which particles or colloids of a starting material of a film components is dispersed in a solvent, on a substrate; a gelling treatment portion which is disposed in neighborhood of this coated portion and gels the particles or the colloids in the coated film formed on the coated portion; a plurality of pre-treatment portions for pre-treating prior to coating of the coating liquid on the substrate; a plurality of heating portions for drying the substrate after treatment at the gelling treatment portion; a receiving portion receiving the substrate from the outside; a main transfer portion which, in addition to transferring to the coating portion through the pre-treatment portion after reception of the substrate from the receiving portion, transfers the substrate after treatment at the gelling treatment portion to the heating portion; and an auxiliary transfer portion transferring the substrate coated at the coating portion to the gelling treatment portion.
According to the seventh invention, the substrate is transferred by an exclusive auxiliary transferring portion from the coating portion to the gelling treatment portion. Therefore, the substrate, immediately after the coating liquid is applied, is transferred to the next step, thereby evaporation of the solvent can be suppressed, resulting in a thin film of excellent film quality.
Here, in the aforementioned apparatus for forming a film, on the transferring path of the substrate in the auxiliary transferring portion, a means for feeding vapor of solvent component, for instance, ethylene glycol, can be provided with. Further, a case for covering the coating portion and gelling treatment portion, and a means for feeding vapor of the solvent component into the case may be provided with. In this case, evaporation of the solvent in the coated film during transferring of the substrate can be further suppressed.
In the aforementioned apparatus for forming a film, a solvent replacement treatment portion which is disposed neighboring the gelling portion, supplies another solvent different from the aforementioned solvent to the substrate treated at the gelling treatment portion, and replaces the solvent in the coated film by another solvent, can be provided, and the substrate treated at the gelling treatment portion may be transferred to the solvent replacement treatment portion by an auxiliary transferring portion. In this case, since the time period during which large surface tension of the solvent is added on the reticular structure of TEOS is made short, collapse of the film structure is suppressed, resulting in a thin film of excellent quality.